This invention relates to an optical disk device for use in driving an optical disk, such as compact disk (CD), digital versatile disk (DVD), or the like.
In order to make a highly integrated optical disk, a laser beam spot is made small in size by shortening a wavelength of the laser beam and making (NA) of an objective lens large. For example, high integration is thereby achieved in a recently normalized DVD based on a normalization of CD which is widely used nowadays. Such a DVD and a CD have the same diameters and thickness of the disks therebetween. It is possible that a driving unit for rotating the disks and a loading unit for containing the disks are commonly used between the DVD and the CD. From the perspectives of a manufacturing cost and a mounting space, it is desirable that an optical disk device be applied not only to the DVD but also to the CD. Moreover, it is further desirable that an optical disk device can be commonly applied to different disks which are similar to each other in disk diameters, wavelength of lazer beams, and writing systems thereof. For this purpose, various techniques are proposed conventionally. Within the techniques, the highest compatibility is provided by such an optical disk device having a plurality of optical heads applicable to differently normalized optical disks, respectively.
An example of such a conventional optical disk device having a plurality of optical heads is disclosed in Unexamined Japanese Patent Publication 297909/1996. The conventional optical disk device disclosed in the above-referenced paper comprises a rotating and driving unit for supporting and driving an optical disk, a plurality of optical heads applicable to differently normalized optical disks, respectively to write and read the optical disks, guiding members equal to the optical heads in number for guiding each optical head along different radial directions of the optical disks, and a pushing member for pushing a guiding operation by each guiding member. In the optical disk device, the pushing member moves to a predetermined position so as to bring each optical head to a desired position.
However, the conventional optical disk device inevitably becomes large in size, since the guiding members therein are required to be equal in number to the optical heads.